The American Heart Association recommends parents limit their children's exposure to screens to no more than one to two hours a day to prevent risk of obesity and heart disease, but a 2016 Nielsen poll found that the average American spends 11 hours a day in front of some kind of digital screen.
In July, researchers at the University of Toledo in Ohio warned in the journal Scientific Reports that prolonged exposure to blue light — a high-intensity 445-nanometer shortwave emitted from digital screens, the sun and other electronic devices — can accelerate blindness and increase risk of eye disease.
"Photoreceptors are like the vehicle. Retinal is the gas," study author Ajith Karunarathne told Popular Science, explaining that blue light causes the retinal to oxidize and create "toxic chemical species," killing photoreceptor cells. If photoreceptors are the vehicle and retinal is the gas, blue light is akin to the spark, he said.
Karunarathne and his team conducted multiple cell culture tests in the lab to test "whether retinal or blue light excited retinal, independent of photoreceptors, elicits PIP2 hydrolysis and inositol (1,4,5) triphosphate (IP3) generation in cells." Such messenger molecules are part of calcium's regulatory pathways and are considered key players of cytotoxicity in the retina, according to the study.
"We are being exposed to blue light continuously, and the eye's cornea and lens cannot block or reflect it," Karunarathne said in a university article. "No activity is sparked with green, yellow, or red light. The retinal-generated toxicity by blue light is universal. It can kill any cell type."
Related: Study: The amount of time kids spend on mobile screens has tripled in 4 years
With the killing of photoreceptor cells, which don’t grow back when damaged, there’s an increased risk of age-related mascular degeneration, an incurable eye disease that leads to significant vision loss after age 50.“You need a continuous supply of retinal molecules if you want to see,” Karunarathne said. “Photoreceptors are useless without retinal, which is produced in the eye.”
The University of Toledo's findings directly counter what the American Academy of Ophthalmology reported last year — that blue light from our devices doesn't actually cause eye damage.
But Karunarathne and his team plan to continue collecting data on prolonged exposure to blue light on our eyes.
“Who knows. One day we might be able to develop eye drops, that if you know you are going to be exposed to intense light, you could use some of those… to reduce damage,” he said.
For now, he recommends wearing sunglasses that filter both UV and blue light outdoors and avoiding screen time in the dark.
Most smartphones also offer built-in blue light filters. For iPhones, you can turn your phone on “Night Mode” to turn the filter on, and on Android, your settings will offer an option to turn the blue light filter on.
Both Apple and Android allow users to schedule blue light filters for specific times.
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